Integrated hydroxyl radicals and hot water pretreatment (IHRHW) was employed in the bioconversion of the brown macroalgae Macrocystis pyrifera (M. pyrifera) in this study. The optimum experimental pretreatment condition (100 ℃, 30 min, 11.9 mM FeSO₄) and the predicted optimum pretreatment condition (113.95 ℃, 29.1 min, 12.75 mM FeSO₄) were identified using a central composite design method. M. pyrifera attained 100% carbohydrate recovery, and hydroxymethylfurfural and furfural were not formed after the new pretreatment process. The IHRHW-treated macroalgae digestibility reached 88.1% under the optimum experimental condition, whereas that under the predicted optimum condition reached 92.1%. The value was approximately threefold higher than those obtained with untreated M. pyrifera. FT-IR spectroscopy and XRD analysis results showed that IHRHW pretreatment could disrupt the hydrogen bonds and crystalline of cellulose in macroalgae, which was benefit for the hydrolysis of cellulose by cellulase.

The Dr. Le Gao and M.S. Feng Gao are two co-first authors of the paper. Dr. Dongyuan Zhang, Dr. Shulin Chen and Dr. Demao Li are contributed to the final draft of the manuscript. This work was supported by the Tianjin Science and Technology Support Key Project Plan (12ZCZDSFO2000 and 12ZCZDSY12300) and the Hi-Tech Research and Development Program (863) of China (2012AA052103).